I could live with it if they did ads comicbook style. Throw in a random page of adds every now and then. But I'd expect the price to be significantly lower and have a non-ads ebook available for realistic prices.

But if this happens, I'd hate to see them implement this, say an ebook with ads costs $4.99-9.99, and then justify that an ebook with no ads costs $9.99-19.99 all of a sudden. Unfortunately, companies love this tactic. :/